1. Field of the Invention
The present invention generally relates to intravascular devices for treating certain medical conditions and, more particularly, relates to a low profile intravascular occlusion devices for treating congenital defects including Atrial and Ventricular Septal Defects (ASD and VSD respectively), Patent Ductus Arteriosus (PDA) and Patent Foramen Ovale (PFO) as well as conditions that result from previous medical procedures such as Para-Valvular Leaks (PVL) following surgical valve repair or replacement. The devices made in accordance with the invention are particularly well suited for delivery through a catheter or the like to a remote location in a patient's heart or in analogous vessels or organs within a patient's body.
2. Description of the Related Art
A wide variety of intra cardiac prosthetic devices are used in various medical procedures. For example, certain intravascular devices, such as catheters and guide wires, are generally used simply to deliver fluids or other medical devices to specific locations within the vascular system of a patient, such as a selective coronary artery. Other, frequently more complex, devices are used in treating specific conditions, such as devices used in removing vascular occlusions or for treating septal defects and the like.
In certain circumstances, it may be necessary to occlude a patient's vessel, such as to stop blood flow through an artery to a tumor or other lesion. Presently, this is commonly accomplished simply by inserting, for example, Ivalon particles (a trade name for vascular occlusion particles) and short sections of coil springs into a vessel at a desired location. These “embolization agents” will eventually become lodged in the vessel, frequently floating downstream of the site at which they are released before blocking the vessel. This procedure is often limited in its utility, in part, due to the inability to precisely position the embolization agents. These embolization agents are not commonly used as an intra cardiac occluding device.
Physicians may temporarily occlude a septal defect until the patient stabilizes enough for open-heart surgical procedures and have used balloon catheters similar to that disclosed by Landymore et al. in U.S. Pat. No. 4,836,204. When using such a catheter, an expandable balloon is carried on a distal end of a catheter. When the catheter is guided to the desired location, the balloon is inflated with a fluid until it substantially fills the defect and becomes lodged therein. Resins, which will harden inside the balloon, such as an acrylonitrile, can be employed to permanently fix the size and shape of the balloon. The balloon can then be detached from the end of the catheter and left in place. If the balloon is not filled enough, it will not be firmly lodged in the septal defect and may rotate and loosen from the septal wall, thereby being released into the blood flowing from the right or left ventricular chamber. Overfilling the balloon is an equally undesirable occurrence, which may lead to the rupture of the balloon and release of resins into the patient's bloodstream.
Mechanical embolization devices, filters and traps have been proposed in the past, representative examples of which are disclosed in King et al., U.S. Pat. No. 3,874,388 (the '388 patent), Das, U.S. Pat. No. 5,334,217 (the '217 patent), Sideris, U.S. Pat. No. 4,917,089 (the '089 patent) and Marks, U.S. Pat. No. 5,108,420 (the '420 patent). The '388, '217, '089, and '420 devices are typically pre-loaded into an introducer or delivery catheter and are not commonly loaded by the physician during the medical procedure. During deployment of these devices, recapture into the delivery catheter is difficult if not impossible, thereby limiting the effectiveness of these devices.
Significantly, the size of these devices is inherently limited by the structure and form of the device. When using occluding devices, such as in the above-identified '089, '388, '217, or '420 patent (plugs to occlude septal defects), the pressure and therefore the chance of dislodgment of the device increases with the size of the defect. Consequently, these devices must have a very large retention skirt positioned on each side of the defect. Oftentimes, the position of the septal defect dictates the size of the retention skirt. In a membranous type septal defect, it is difficult, if not impossible to be able to effectively position the '388, '217, '089, or '420 device without at least partially closing off the aorta. Also, these disclosed devices tend to be rather expensive and time-consuming to manufacture. Hence, it is desirable to provide a low profile device that is recoverable and retractable into the delivery system without increasing the overall thickness of the device. The desired device should also be made with a relatively small retention skirt so as to be positionable within a membranous type septal defect without closing off the aorta.
It the case of a membranous ventricular septal defect, if the central diameter of the occluder is exerting too much pressure on the septum, heart block may occur, and if the retention skirt is too large, it may interfere with the opening and closing of the aortic valve. The stiffness required to retain the current devices in place against blood pressure makes them more difficult to deliver. Hence, there is a need for a low profile, easy to deliver device, that can be shaped for retention without blocking off the aorta or aortic valve and which is conformable without exerting excess pressure on tissue near conductive pathways.
It the case of PDA's, a smaller, lower profile device that can fit through a 4 French catheter potentially allows treatment of pre-mature infants with a PDA. These patients are current sent to surgery because the use of coils to occlude the PDA, are not suitable due to the size of the PDA anatomy.
Also, the shape of the prior art devices (for example, squares, triangles, pentagons, hexagons and octagons) requires a larger contact area, having corners, which extend to the free wall of the atria. Each time the atria contracts (approximately 100,000 times per day), internal wires within the prior art devices, such as described in the Das '217 patent, are flexed, creating structural fatigue fractures in approximately 30 percent of all cases. The sharp corners of these devices resulted in a high percentage of cardiac perforations and they were, therefore, withdrawn from the market. Furthermore, the previous devices require a 14-16 French introducing catheter, making it impossible to treat children affected with congenital defects with these devices.
Accordingly, it would be advantageous to provide a reliable occlusion device which is both easy to deploy through a 4-7 French catheter and which can be accurately placed in a vessel or organ. It would also be desirable to provide a low-profile recoverable device for deployment in an organ of a patient's body.
In the Kotula et al. U.S. Pat. No. 5,846,261, there is described a reliable, low-profile, intra cardiac occlusion device which may be formed to treat, for example, Ventricular Septal Defects (VSD), Atrial Septal Defects (hereinafter ASD), and Patent Ductus Arteriosus (hereinafter PDA). When forming these intravascular devices from a resilient metal fabric, a plurality of resilient strands exhibiting a memory property are provided, with the wires being formed by braiding to create a resilient material. This braided fabric is then deformed to generally conform to a molding surface of a molding element and the braided fabric is heat treated in contact with the surface of the molding element at an elevated temperature. The time and temperature of the heat treatment is selected to substantially set the braided fabric in its deformed state. After the heat treatment, the fabric is removed from contact with the molding element and it will substantially retain its shape in the deformed state. The braided fabric so treated defines an expanded state of a medical device, which can be deployed through a catheter into a channel in a patient's body.
Embodiments of the Kotula et al. invention provide specific shapes for medical devices, which may be made in accordance with that invention to address identified medical needs and procedures. The devices have an expanded low-profile configuration and may include recessed clamps that gather and hold the ends of the braided metal fabric to prevent unraveling and that attach to an end of a delivery device or guide wire, allowing recovery of the device after placement. In use, a guide catheter is positioned and advanced in a patient's body such that the distal end of the catheter is adjacent a desired treatment site for treating a physiological condition. A preselected medical device, made in accordance with the Kotula et al. invention and having a predetermined shape, is then collapsed by longitudinally stretching and is inserted into the lumen of the catheter. The device is urged through the catheter and out the distal end whereupon, due to its memory property, it will tend to substantially return to its expanded, relaxed state adjacent the treatment site. The guide wire or delivery catheter is then released from the clamp and removed.
In accordance with a first of these embodiments, a generally elongate medical device has a generally tubular middle portion and a pair of expanded diameter portions, with one expanded diameter portion positioned at either end of the middle portion. The length of the middle portion approximates the wall in which the thickness of the defect to be occluded is formed. The center of at least one of the expanded diameter portions may be concentric with or offset relative to the center of the middle portion, thereby allowing occlusion of a variety of septal defects including membranous type ventricular septal defect, while providing a retention skirt of sufficient size to securely close the abnormal opening in the septum. As mentioned above, each braided end of the device is held together with a clamp. The clamps may be recessed into the expanded diameter portion of the device, thereby reducing the overall length dimension of the device and creating a low profile occluder.
In another embodiment of the Kotula et al. invention described in the '261 patent, the medical device is generally bell-shaped, having an elongate body, a tapered first end, and a larger flanged second end. The second end has a fabric disc which will be oriented generally perpendicular to an axis of a channel when deployed therein. The clamps, which hold together the braided strand ends, are recessed toward the center of the “bell” providing a low-profile device having a reduced overall height dimension.
The ability of the devices described in the Kotula et al. '261 patent to occlude abnormal openings in a vascular organ depend upon the pick size of the braided structure which, in turn, depends upon the number of wire strands used in the braid. However, a practical limit exists on just how many such strands can be braided. For example, if 72 bobbins are used on the braiding machine, the resulting pick size is such that a prolonged period of time must elapse before total thrombosis takes place and blood flow through the device is totally occluded. Even with 144 bobbins, blood flow is not immediately stemmed. If the pick size were effectively halved by doubling the number of bobbins on the braiding machine to 288, occlusion would occur somewhat instantaneous upon placement of the medical device in the abnormal opening. However, the resulting braiding machine becomes impractical from a size and cost standpoint.
As a way of reducing the time required to achieve total occlusion, the Kotula et al. '261 patent teaches the concept of filling the interior of the medical device with an occluding fiber or an occluding fabric, such as a polyester fabric. This occluding fiber material or fabric is generally hand sewn in place, which adds significantly to the manufacturing cost of the medical devices. Perhaps more importantly, adding polyester fiber or fabric in the interior of the device interferes with the ability to reduce the effective diameter of the device upon stretching prior to loading the device into the lumen of a delivery catheter. It should be recognized that by reducing the size of the delivery catheter, it can be used with smaller patients.
Thus, a need exists for a way to form a collapsible medical device for occluding abnormal openings in a vascular organ which provides rapid occlusion following delivery and placement thereof and which does not require the addition of an occluding fabric placed within the interior of the medical device as taught by the prior art.
Another limitation of the bell-shaped occlusion device described in the Kotula et al '261 patent regards its use in occluding a Patent Ductus Arteriosus (PDA) This passage way between the pulmonary artery and the aorta is variable in diameter and length and the passageway is not always perpendicular to the connected vessels. The design of the bell-shape occlusion device is such that the rim at one end of the device placed in the higher pressure aortic side may project into the aorta when the passage is not perpendicular to the aortic wall. The bell-shaped design also does not accommodate passageway length and route variation ideally and it is possible for the device to partially extrude out of the PDA. A further limitation is that the device must be delivered from the more difficult to reach pulmonary artery side of the PDA. This is due to the arterial sheath size being larger than the femoral artery in young patients. For infants, there is a need for a PDA occluder design that is low in profile that can be delivered through a 4 French catheter that allows for a venous delivery in premature infants and an arterial approach in premature infants weighing more than 1.5-2 kg. The advantage of a venous approach for PDA closure is to potentially treat infants as small a 1 kg. The advantage of an arterial approach in slightly larger premature infants is that both angiography and device implant can take place from a common access point in the femoral artery.
There is also a need for an improved occlusion device (occluder) for closing the PDA that allows for: improved security of placement; improved accommodation of diameter, length, and pathway variation; minimal projection into the flow stream of the pulmonary and aortic arteries; and for improved ease of placement from the aortic side by femoral artery access in addition to the previous pulmonary artery access.
In treating damaged or diseased heart valves such as the mitral or aortic valve, it is often necessary to surgically repair or replace the valve with a tissue or mechanical valve. These valves generally have a fabric cuff surrounding the valve at the base. The surgeon uses suture to sew tissue, adjacent the valve base, to the cuff to hold the valve in place. For a number of reasons, the suture may occasionally pull out from weak tissue or suture may break or suture may not have been sewn ideally. In any event this loss of connective tissue to the valve cuff results in open holes (para-valvular leak, PVL) along the cuff causing valve leakage and poor valve performance from regurgitation of blood between the ventricle and the atrium and a lowering of blood pressure. These open areas may be round, oval or crescent shaped and must be closed by surgical or other means. Today there is no ideal means of closing these valve leaks other than by surgery. Attempts have been made by physicians to deploy devices as herein described by the Kotula el al '261 patent but this device has not been ideal for such variable sized and shaped leaks. One of the most time consuming aspects of a percutaneous endoluminal approach to closing a PVL is locating the closure device in the hole along the valve cuff.
Since the current devices are not steerable, it would be preferable that the device be delivered over a guidewire that can be more easily directed across the leak prior to placing the device. An alternative approach would be placing the device through a steerable tip sheath.
Therefore, an additional need exists for a method for percutaneous treatment of para-valvular leaks by use of an improved occlusion device that can be easily delivered over a guide wire or by a steerable sheath, in a low profile catheter based delivery system and which easily accommodates the variety of leak passageway shapes and sizes typical of such valve leakage cases without interfering with valve leaflet function.
The present invention provides a readily manufacturable solution to the aforementioned problems inherent in the prior art as represented by the Kotula et al. '261 patent.